package com.jiandp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.jiandp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.jiandp.utils.RedisConstants.*;
@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit timeUnit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,timeUnit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit){
        //设置逻辑过期
        RedisData redisData  =new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit){
        //1.从redis中查询店铺缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)){
            //3.存在返回数据

            return JSONUtil.toBean(json, type);
        }
        if (json!=null){
            return null;
        }

        //4.不存在，查询数据库
        R r = dbFallback.apply(id);
        if (r == null) {
            //5.不存在返回错误
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;

        }
        //6.存在，查询并建立缓存
        this.set(key,r,time,unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID>R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time, TimeUnit unit){
        //1.从redis中查询店铺缓存
        String key = CACHE_SHOP_KEY + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)){
            //3.存在返回数据
            return null;
        }
        //4 命中需要把Json反序列化成对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1 未过期直接返回数据
            return r;
        }

        //5.2 过期需要缓存重建
        //6缓存重建
        //6.1获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2判断获取锁其否成功
        if (isLock){
            // 【Double Check】再次检查缓存是否已被其他线程重建
            String latestShopJson = stringRedisTemplate.opsForValue().get(key);
            if (StrUtil.isNotBlank(latestShopJson)) {
                RedisData latestRedisData = JSONUtil.toBean(latestShopJson, RedisData.class);
                if (latestRedisData.getExpireTime().isAfter(LocalDateTime.now())) {
                    // 用泛型 type 反序列化，而非固定 Shop.class
                    R latestR = JSONUtil.toBean((JSONObject) latestRedisData.getData(), type);
                    unLock(lockKey);
                    return latestR;
                }
            }
            //6.3成功，开启独立线程实施缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                   R r1 = dbFallback.apply(id);
                   this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }

            });
        }

        //6.4失败返回过期的商品信息

        //7.返回
        return r;
    }


    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void  unLock(String key){
        stringRedisTemplate.delete(key);
    }



}
